MICROSATELLITE POLYMORPHISM ANALYSIS ALLOWS THE INDIVIDUAL ASSIGNMENTOF THE RAT 11-BETA-HYDROXYLASE GENE (CYP11B1) AND THE RAT ALDOSTERONESYNTHASE GENE (CYP11B2) TO CHROMOSOME-7 USING RAT X MOUSE SOMATIC-CELL HYBRIDS AND IDENTIFIES DIFFERENCES BETWEEN AND WITHIN VARIOUS RAT STRAINS

Mouse hepatoma x rat hepatocyte hybrids that segregate rat chromosomes were used to determine the chromosomal location of the rat genes enco ding 11 beta-hydroxylase and aldosterone synthase (Cyp11b1 and Cyp11b2 respectively). By means of species-specific restriction fragments and microsatellite markers both genes were mapped to rat chromosome 7. Th e Cyp11b1 microsatellite marker was subsequently found to vary in leng th between and within rat strains. Furthermore, we compared the sequen ces of Cyp11b1 markers in two genetically hypertensive strains of rat with their normotensive counterparts. Previous studies have indicated that 11 beta-hydroxylase activities in Milan and Lyon hypertensive str ains are different from their respective genetic controls. The Cyp11b1 microsatellite regions from Lyon hypotensive and normotensive strains of rat were similar and were both shorter by 15 bases than that of th e Lyon hypertensive strain. The Cyp11b1 marker in Milan hypertensive ( MHS) and normotensive (MNS) strains differ from all the Lyon strains a nd from each other. The MHS marker is 12 bases shorter than that of MN S rats. These differences in microsatellite length may provide useful polymorphic markers in cosegregation studies of genetic hypertension i n rats.